For everyone that is curious why the non-M bar doesn't fit, it's because of the mounting tabs. The M rear swaybar is attached by 2 bolts (Similar to how the front swaybar is) to the rear subframe. The non-M uses 1 bolt and a slip tab.

It is possible to use an M rear swaybar on a non-M, but you will need to have the stock rear swaybar mounts cut, and have a steel plate welded on for the M bar to mount onto. For the trouble, you're better off picking up a complete front and rear swaybar kit from TMS or the like...